A few months ago here at SolarWinds we released a new add-on module to Orion called the Orion IP SLA Manager. The IP SLA manager leverages Cisco IP SLA and other protocols to measure and report on network performance from different perspectives across the network and to provide VoIP device and quality of service management. This new module has a very flexible licensing structure and is not tied to the version of Orion NPM (SLX, SL2000, SL500, SL250, SL100) that you own but instead is based on the number of IP SLA devices that you're going to run IP SLA operations from.
While this sounds well and good and makes a lot of sense to geeks like me that have been intimately involved with IP SLA for years, if you're just now learning about IP SLA you may be wondering a) just what the heck is IP SLA? and b) how do I estimate the number of IP SLA devices I'll be using?
What is Cisco IP SLA
Cisco IP SLA is a groovy feature within Cisco IOS that allows you to configure your Cisco IOS devices to run tests from their location on the network. These tests are called operations and can be as simple as having a router ping the other routers in your network or more complex like having the router measure VoIP quality between it and another IP SLA capable device. The results of these tests are stored in memory on the router. You can either access the results from the CLI or, preferrably, have a network management application like the Orion IP SLA Manager retrieve and consolidate these results into easy to use dashboards, charts, reports, and alerts.
How do I estimate the number of IP SLA devices I'll use?
Estimating the number of IP SLA devices that you'll use is easy. Basically, any place on the network that you want to understand network performance from will be a place where you'll want to enable IP SLA. If you're an all Cisco shop, I'd just estimate the total number of Cisco devices and divide by 2. If you've got a mix of Cisco gear and other stuff as well, I'd increase the number to about 80% of the Cisco devices you've got. The great thing is that the better IP SLA tools like the Orion IP SLA Manager configure and manage the operations for you, so rolling it out even to hundreds of devices is painless.
As an example, let's assume that you're an all Cisco shop. At every juntion point on the network where you'd like to measure network performance from you'll want to enable IP SLA. So, for every location on your WAN you'll want to have an IP SLA enabled device. Additionally, anywhere that performance may vary greatly you'll want to measure from. Some folks measure from one device per location and one device per subnet or VLAN. This way, if you have performance variation in your data center or is someone mucks up an ACL that's only affecting traffic within the site you'll know about it.
Let me know if you'd like to hear more about this or if you have questions about deploying IP SLA in your environment.
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